#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
 struct ListNode {
 	int val;
 	struct ListNode *next;
  };
struct ListNode* FindKthToTail(struct ListNode* pListHead, int k) {
    struct ListNode* fast = pListHead;
    struct ListNode* slow = pListHead;
    while (k--) {
        if (fast == NULL)
            return NULL;
        fast = fast->next;
    }
    while (fast) {
        fast = fast->next;
        slow = slow->next;
    }
    return slow;
}
int main() {
    struct ListNode* n1 = (struct ListNode*)malloc(sizeof(struct ListNode));
    struct ListNode* n2 = (struct ListNode*)malloc(sizeof(struct ListNode));
    struct ListNode* n3 = (struct ListNode*)malloc(sizeof(struct ListNode));
    struct ListNode* n4 = (struct ListNode*)malloc(sizeof(struct ListNode));
    n1->val = 1;
    n2->val = 2;
    n3->val = 3;
    n4->val = 4;
    n1->next = n2;
    n2->next = n3;
    n3->next = n4;
    n4->next = NULL;
    struct ListNode* s = FindKthToTail(n1,2);
    printf("%d ", s->val);
    return 0;
}